Ca2+, Calmodulin‐Dependent Regulation of Microtubule Formation via Phosphorylation of Microtubule‐Associated Protein 2, τ Factor, and Tubulin, and Comparison with the Cyclic AMP‐Dependent Phosphorylation

Hideyuki Yamamoto, Kohji Fukunaga, Satoshi Goto, Etsuro Tanaka, Eishichi Miyamoto

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156 Citations (Scopus)

Abstract

Abstract: Isolated microtubule‐associated protein 2 (MAP2), τ factor, and tubulin were phosphorylated by a purified Ca2+, calmodulin‐dependent protein kinase (640K enzyme) from rat brain. The phosphorylation of MAP2 and τ factor separately induced the inhibition of microtubule assembly, in accordance with the degree. Tubulin phosphorylation by the 640K enzyme induced the inhibition of microtubule assembly, whereas the effect of tubulin phosphorylation by the catalytic subunit was undetectable. The effects of tubulin and MAPs phosphorylation on microtubule assembly were greater than that of either tubulin or MAPs phosphorylation. Because MAP2, τ factor, and tubulin were also phosphorylated by the catalytic subunit of type‐II cyclic AMP‐dependent protein kinase from rat brain, the kinetic properties and phosphorylation sites were compared. The amount of phosphate incorporated into each microtubule protein was three to five times higher by the 640K enzyme than by the catalytic subunit. The Km values of the 640K enzyme for microtubule proteins were four to 24 times lower than those of the catalytic subunit. The peptide mapping analysis showed that the 640K enzyme and the catalytic subunit incorporated phosphate into different sites on MAP2, τ factor, and tubulin. Investigation of phosphoamino acids revealed that only the seryl residue was phosphorylated by the catalytic subunit, whereas both seryl and threonyl residues were phosphorylated by the 640K enzyme. These data suggest that the Ca2+, calmodulin system via phosphorylation of MAP2, τ factor, and tubulin by the 640K enzyme is more effective than the cyclic AMP system on the regulation of microtubule assembly.

Original languageEnglish
Pages (from-to)759-768
Number of pages10
JournalJournal of Neurochemistry
Volume44
Issue number3
DOIs
Publication statusPublished - 1985 Jan 1
Externally publishedYes

Keywords

  • Brain
  • Ca
  • Microtubule assembly
  • Microtubule‐associated protein 2
  • Tubulin
  • calmodulin‐dependent protein kinase
  • τ Factor

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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